docs: def search_point(self, point, result):
          """
          Returns all intervals that contain point.
          """
          for k in self.s_center:
              if k.begin <= point < k.end:
                  result.add(k)
          if point < self.x_center and self[0]:
              return self[0].search_point(point, result)
          elif point > self.x_center and self[1]:
              return self[1].search_point(point, result)
          return result